If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

How can you leave a room with two legs and return with six legs?

When we see 2 but call 10?

Find the number of squares in the below picture

Can you place six X (crosses) in below board without making three in a row in any way ?

Three people enter a room and have a green or blue hat placed on their heads. They cannot see their own hat but can see the other hats.
The colour of each hat is purely random. They could all be green, blue, or any combination of green and blue.
They need to guess their own hat colour by writing it on a piece of paper, or they can write 'pass'.
They cannot communicate with each other in any way once the game starts. But they can have a strategy meeting before the game.
If at least one of them guesses correctly they win $10,000 each, but if anyone guesses incorrectly they all get nothing.
What is the best strategy?

Can you write down eight eights so that they add up to one thousand?

Find the next number in the sequence

1, 2, 6, 21, 88, __?

Complete the given grid with valid words. You can only use the letters AAEEIIMMPPTT.

Hint: The grid reads the same across as down.